1. Field of the Invention
The present invention relates generally to an optical lens, and more particularly to a miniature image pickup lens.
2. Description of the Related Art
With the thriving development of portable devices, the market demand for digital image capture modules are continuously growing. In consideration of portability and convenience, it is commonly expected that the digital image capture modules will become smaller and lighter without sacrificing the image quality.
There are two main types of image sensors applied on the conventional image capture modules, which are charge coupled device (CCD) and complementary metal oxide semiconductor (CMOS). CMOS has become the most widely used image sensors in the market of portable devices because of its low cost, low power consumption, and high integration. In addition, due to the advancement in semiconductor manufacturing technology, the size of a pixel has greatly reduced, and therefore an image sensor is able to provide images with higher resolution. But the reduction of pixel size also means that the luminosity captured by an image sensor is less, so some kind of systems of lenses are needed to increase luminosity to reduce the influences of noises.
Along with these image devices becoming smaller, the sizes of aforementioned image capture devices and the lenses applied on the aforementioned image devices are greatly reduced too. The lenses for such image capture modules are requested to have smaller size and higher optical performance as well. As a result, size and optical performance are two indispensable considerations for the lenses of image devices.
Besides, the lenses with small sizes used in image devices are being developed towards wider angles, but such wide-angled systems tend to have problems of distortion and chromatic aberration. Moreover, in consideration of lowering cost, the manufacturers usually use plastic lenses instead of glass ones, but the plastic lenses are more sensitive to temperature, so that the image capture modules with plastic lenses are easily affected by fluctuations of temperature, and have the defect of unstable image quality.